1. Field
The present disclosure generally relates to systems and methods of vectoring the exhaust of a fan, particularly for an aircraft lift engine.
2. Description of the Related Art
Aircraft that can hover, take off and land vertically are commonly referred to as Vertical Take-Off and Landing (VTOL) aircraft. This classification includes fixed-wing aircraft as well as helicopters and aircraft with tiltable powered rotors. Methods of vectoring the vertical lift airflow have included nozzles that can be swiveled in a single direction and the use of two sets of flat flapper vanes arranged 90 degrees to each other and located at the external nozzle.
The F-35 Lightning shown in FIG. 1 is a current aircraft that has VTOL capability. The propulsion system, shown in FIG. 2, provides vertical lifting force using a combination of vectored thrust from the turbine engine and a vertically oriented lift fan. The lift fan is located behind the cockpit in a bay with upper and lower clamshell doors. The engine exhausts through a three-bearing swivel nozzle that can deflect the thrust from horizontal to just forward of vertical. Roll control ducts extend out in each wing and are supplied with their thrust with air from the engine fan. Pitch control is effected via lift fan/engine thrust split. Yaw control is through yaw motion of the engine swivel nozzle. Roll control is provided by differentially opening and closing the apertures at the ends of the two roll control ducts.
The lift fan has a telescoping “D”-shaped nozzle to provide thrust deflection in the forward and aft directions, as shown in FIG. 3. The D-nozzle has fixed vanes at the exit aperture.